1. Field of the Invention
The present invention relates to an ink cartridge (ink tank) configured to store ink (e.g., pigment ink) having particles of a color material that are easily precipitated, and in particular, to an ink cartridge having ink agitation unit, and a printer on which the ink cartridge can be mounted.
2. Description of the Related Art
Conventionally, ink used for an inkjet printer includes dye ink using dye for a color material and pigment ink using pigment for the color material.
A printed matter using the pigment ink has high weathering resistance or high water resistance. On the other hand, the pigment ink has a problem of an uneven density in printing to be solved. The phenomenon may occur at the start time of using new ink or when the ink is not used for a relatively long time as particles of the pigment are easily precipitated in the ink, and a pigment density becomes lower at an upper portion of the ink cartridge and the pigment density becomes higher at a lower portion of the ink cartridge.
As a countermeasure therefor, Japanese Patent Application Laid-Open No. 2005-66520 discusses an ink tank in which an ink supply portion is arranged to one edge of an envelope-shaped ink storage bag, an agitation member is arranged to another edge opposite to the one edge to be operated with external power, and an operation portion for operating the agitation member is externally extended to the ink storage bag. By operating the operation portion, a joint portion, at which the agitation member and the edge of the ink storage bag are joined, functions as a fulcrum point. Further, the agitation member inserted to the ink storage bag is moved to agitate the pigment ink.
With the configuration discussed in Japanese Patent Application Laid-Open No. 2005-66520, a tank casing is provided with an ink supply portion arranged on the edge of the ink storage bag opposite to the edge on which the agitation member is arranged. As a consequence, the movement of the ink storage bag is regulated (limited) on the ink supply unit side. In particular, when the amount of ink in the ink storage bag becomes small and the ink storage bag is reduced in volume to become flattened, the operation of the agitation member in the ink storage bag is inhibited, and an agitation effect is deteriorated.
When manufacturing an ink storage bag having a spout and an agitation member on opposite edges, the spout needs to be attached to one opening of a cylindrical-shaped film and the agitation member needs to be attached to the other opening. Therefore, an attachment process becomes complicated because the attachment of the spout and the agitation member is performed at opposite positions, respectively. The possibility is high to generate undesirable creases or crimping due to the attachment. Consequently, the possibility of an adverse effect such as leakage of the ink is increased.
In addition, the ink supply unit is generally arranged at the back of a tank attachment operation range. An agitation mechanism for operating the agitation member is arranged in front of the tank attachment operation range. The printer configuration is complicated and is increased in scale.